Vacuum pump and vacuum pump constituent component

ABSTRACT

The present disclosure provides a vacuum pump of which a thermal resistance between a heater and a water-cooling tube is high and which has a small number of components. The vacuum pump includes: a main body casing having an intake portion and an exhaust portion of gas; a turbo-molecular pump mechanism portion in which stator blades and rotor blades are formed; and a motor for rotating the rotor blades, wherein the main body casing has a base spacer capable of thermal conduction between a heating spacer portion and a water-cooling spacer portion having been integrally molded, and the base spacer is provided with a boundary portion having been molded such that a cross section thereof assumes a narrow neck shape between the heating spacer portion and the water-cooling spacer portion.

This application is a U.S. national phase application under 35 U.S.C. § 371 of international application number PCT/JP2020/011072 filed on Mar. 13, 2020, which claims the benefit of priority to JP application number 2019-058859 filed on Mar. 26, 2019. The entire contents of each of international application number PCT/JP2020/011072 and JP application number 2019-058859 are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a vacuum pump such as a turbo-molecular pump and to a constituent component of the vacuum pump.

BACKGROUND

Generally, a turbo-molecular pump is known as one type of a vacuum pump. The turbo-molecular pump is configured to rotate a rotor blade by energizing a motor inside a pump main body and exhaust gas (process gas) having been sucked into the pump main body by blowing away a particle of the gas. In addition, some types of turbo-molecular pumps are provided with a heater and a cooling tube to appropriately control a temperature of each area inside the pump.

SUMMARY

Since the heater and the cooling tube of a turbo-molecular pump such as that described above are provided in order to realize conflicting functions of heating and cooling, positional relationships and peripheral components must be carefully designed. For example, while a temperature of rotor blades plays a dominant role in a temperature inside a pump, unless a cooling function is designed appropriately, it is difficult to maintain the temperature of the rotor blades and a vicinity thereof at a desired temperature (for example, around 70° C.). In addition, when respective installation locations of the heater and the cooling tube are too close to each other, their respective functions cancel each other out due to heat exchange and makes it difficult to perform temperature control in an efficient manner.

Furthermore, a component for holding the heater and a component for holding the cooling tube (holding components) are usually molded as separate fixtures from the perspectives of a difference in functions, ease of machining, and the like. Therefore, performing temperature control using a heater and a cooling tube increases the number of components and also increases costs required for machining and management of components, assembly of the components, and the like.

An object of the present disclosure is to provide a vacuum pump of which a thermal resistance between a heater and a water-cooling tube (cooling tube) is high and which has a small number of components and to provide a vacuum pump constituent component.

(1) In order to achieve the object described above, a vacuum pump according to the present disclosure includes: a pump mechanism portion in which a stator blade and a rotor blade are formed;

a casing which encloses the pump mechanism portion;

a motor for rotating the rotor blade; and

a vacuum pump constituent component which is capable of thermal conduction between a heating portion and a cooling portion having been integrally molded, wherein

the vacuum pump constituent component is provided with a boundary portion formed so that a cross section thereof assumes a narrow neck shape between the heating portion and the cooling portion.

(2) In addition, in order to achieve the object described above, another vacuum pump according to the present disclosure is the vacuum pump according to (1), wherein the boundary portion is formed between a notched portion on an outer side and a tapered portion on an inner side of the vacuum pump constituent component.

(3) In addition, in order to achieve the object described above, a vacuum pump constituent component according to the present disclosure is capable of thermal conduction between a heating portion and a cooling portion having been integrally molded, wherein the vacuum pump constituent component is provided with a boundary portion molded so that a cross section thereof assumes a narrow neck shape between the heating portion and the cooling portion.

(4) In addition, in order to achieve the object described above, another vacuum pump constituent component according to the present disclosure is the vacuum pump constituent component according to (3), wherein the boundary portion is formed between a notched portion on an outer side and a tapered portion on an inner side.

According to the present disclosure described above, a vacuum pump of which a thermal resistance between a heater and a water-cooling tube is high and which has a small number of components and a vacuum pump constituent component can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a vertical cross section of a turbo-molecular pump according to a first embodiment of the present disclosure.

FIG. 2A is an enlarged view showing a part of the turbo-molecular pump according to the first embodiment, and FIG. 2B is an enlarged view showing another area by changing phases.

FIGS. 3A to 3C are explanatory views showing, side by side from right to left, a heating and cooling structure according to the first embodiment of the present disclosure, a heating and cooling structure according to a second embodiment of the present disclosure, and a conventional structure.

FIG. 4 is an explanatory view showing an outline of temperature control.

DETAILED DESCRIPTION

Hereinafter, vacuum pumps according to respective embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 schematically shows a vertical section of a turbo-molecular pump 10 as a vacuum pump according to a first embodiment of the present disclosure. The turbo-molecular pump 10 is configured to be connected to a vacuum chamber (not illustrated) of an object device such as a semiconductor manufacturing apparatus, an electron microscope, or a mass spectrometer.

The turbo-molecular pump 10 integrally includes a cylindrical pump main body 11 and a box-shaped electric case (not illustrated). In the pump main body 11 among these components, an upper side in FIG. 1 constitutes an intake portion 12 to be connected to a side of the object device and a lower side constitutes an exhaust portion 13 to be connected to an auxiliary pump or the like.

In addition, besides an upright posture in a vertical direction such as that shown in FIG. 1, the turbo-molecular pump 10 can also be used in an upside-down posture, a horizontal posture, and an inclined posture.

While the electric case (not illustrated) houses a power supply circuit portion for supplying power to the pump main body 11 and a control circuit portion for controlling the pump main body 11, detailed descriptions of these components will be omitted here.

The pump main body 11 includes a main body casing 14 which constitutes an approximately cylindrical chassis. The main body casing 14 is constructed by connecting, in series in an axial direction, an intake-side casing 14 a as an intake-side component that is positioned in an upper part in FIG. 1 and an exhaust-side casing 14 b as an exhaust-side component that is positioned on the lower side in FIG. 1. In this case, the intake-side casing 14 a can also be referred to as a casing or the like and the exhaust-side casing 14 b can also be referred to as a base or the like.

The intake-side casing 14 a and the exhaust-side casing 14 b are stacked in a radial direction (a left-right direction in FIG. 1). In addition, in the intake-side casing 14 a, an inner circumferential surface in one end portion (a lower end portion in FIG. 1) in the axial direction opposes an outer circumferential surface in an upper end portion 29 b of the exhaust-side casing 14 b. Furthermore, the intake-side casing 14 a and the exhaust-side casing 14 b are airtightly coupled to each other by a plurality of hexagon socket screws (not illustrated) so as to sandwich an O ring (a sealing member 41) that is housed inside a groove portion.

Roughly speaking, the exhaust-side casing 14 b has a bisected structure made up of a tubular base spacer 42 (a vacuum pump constituent component) and a base body 43 which blocks one end portion (a lower end portion in FIG. 1) in the axial direction of the base spacer 42. In this case, the base spacer 42 and the base body 43 can also be respectively called an upper base and a lower base or the like. While the base spacer 42 has a heating spacer portion 46 and a water-cooling spacer portion 47 which support a heater 48 and a water-cooling tube 49 for a TMS (Temperature Management System), details of the base spacer 42 will be provided later.

The pump main body 11 includes an approximately cylindrical main body casing 14. An exhaust mechanism portion 15 and a rotation driving portion (hereinafter, referred to as a “motor”) 16 are provided inside the main body casing 14. Among these components, the exhaust mechanism portion 15 is a composite-type component made up of a turbo-molecular pump mechanism portion 17 as a pump mechanism portion and a thread groove pump mechanism portion 18 as a thread groove exhaust mechanism portion.

The turbo-molecular pump mechanism portion 17 and the thread groove pump mechanism portion 18 are consecutively arranged in the axial direction of the pump main body 11 and, in FIG. 1, the turbo-molecular pump mechanism portion 17 is arranged on the upper side in FIG. 1 and the thread groove pump mechanism portion 18 is arranged on the lower side in FIG. 1. Hereinafter, basic structures of the turbo-molecular pump mechanism portion 17 and the thread groove pump mechanism portion 18 will be schematically described.

The turbo-molecular pump mechanism portion 17 arranged on the upper side in FIG. 1 transfers gas using a large number of turbine blades and includes stator blades 19 and rotor blades 20 having predetermined inclined or curved surfaces and being formed in a radial pattern. In the turbo-molecular pump mechanism portion 17, the stator blades 19 and the rotor blades 20 are arranged so as to be alternately lined up across approximately ten steps.

The stator blades 19 are integrally provided on the main body casing 14 and rotor blades 20 penetrate between upper and lower stator blades 19. The rotor blades 20 are integrated with a cylindrical rotor 28, and the rotor 28 is concentrically fixed to a rotor shaft 21 so as to cover an outside of the rotor shaft 21. With a rotation of the rotor shaft 21, the rotor blades 20 rotate in a same direction as the rotor shaft 21 and the rotor 28.

In this case, aluminum is adopted as a material of main components of the pump main body 11, and materials of the exhaust-side casing 14 b, the stator blades 19, the rotor 28, and the like to be described later are also aluminum. In addition, in FIG. 1, in order to prevent the drawing from appearing excessively complicated, hatchings that indicate a cross section of components in the pump main body 11 have been omitted.

The rotor shaft 21 is machined into a stepped columnar shape and extends from the turbo-molecular pump mechanism portion 17 to the thread groove pump mechanism portion 18 on the lower side. In addition, the motor 16 is arranged in a center part in an axial direction of the rotor shaft 21. The motor 16 will be described later.

The thread groove pump mechanism portion 18 includes a rotor cylindrical portion 23 and a thread stator 24. The thread stator 24 is also called an “external thread” and the like and aluminum is adopted as the material of the thread stator 24. An outlet port 25 to be connected to an exhaust pipe is arranged in a stage subsequent to the thread groove pump mechanism portion 18, and an inside of the outlet port 25 and the thread groove pump mechanism portion 18 are spatially connected to each other.

The motor 16 described earlier includes rotors (reference sign omitted) fixed to an outer circumference of the rotor shaft 21 and stators (reference sign omitted) arranged so as to surround the rotors. Power for operating the motor 16 is supplied by the power supply circuit portion or the control circuit portion housed in the electric case (not illustrated) described earlier.

Although a detailed illustration and reference signs will be omitted, a contactless bearing (a magnetic bearing) that utilizes magnetic levitation is used to support the rotor shaft 21. Therefore, in the pump main body 11, high-speed rotation is performed in an abrasion-free manner and a long-life environment which eliminates the need for a lubricant is realized. It should be noted that a combination of a radial magnetic bearing and a thrust bearing can be adopted as the magnetic bearing.

Furthermore, protective bearings (also referred to as “touchdown (T/D) bearings”, “backup bearings”, and the like) 32 and 33 in a radial direction are arranged at predetermined intervals around upper and lower parts of the rotor shaft 21. For example, even when problems such as an electrical failure or an atmospheric entry occur, the protective bearings 32 and 33 prevent a position or a posture of the rotor shaft 21 from changing significantly and protect the rotor blades 20 and peripheral portions thereof from damage.

During an operation of the turbo-molecular pump 10 structured as described above, the motor 16 described earlier is driven and the rotor blades 20 rotate. In addition, with the rotation of the rotor blades 20, gas is sucked in from the intake portion 12 shown on the upper side in FIG. 1 and the gas is transferred to a side of the thread groove pump mechanism portion 18 while causing a gas particle to collide with the stator blades 19 and the rotor blades 20. Furthermore, the gas is compressed in the thread groove pump mechanism portion 18, the compressed gas enters the outlet port 25 from the exhaust portion 13, and the gas is exhausted from the pump main body 11 via the outlet port 25.

It should be noted that the rotor shaft 21 as well as the rotor blades 20, the rotor cylindrical portion 23, rotors (reference signs omitted) of the motor 16 that integrally rotate with the rotor shaft 21, and the like can be collectively referred to as, for example, a “rotor portion”, a “rotating portion”, or the like.

Next, a heating and cooling structure that is constituted by the base spacer 42 described earlier and peripheral components thereof will be described. As shown in FIGS. 1, 2A, and 2B, the base spacer 42 is concentrically combined with the base body 43 described earlier and constitutes an exhaust-side area of the main body casing 14. The base body 43 has a stator column 44 which is responsible for supporting the motor 16, the rotor shaft 21, and the like, and the base spacer 42 encloses a proximal end-side circumference of the stator column 44 at a predetermined interval in the radial direction.

As shown partially enlarged in FIG. 2A, the base spacer 42 has a heating spacer portion 46 and a water-cooling spacer portion 47. The base spacer 42 is an integrally molded article formed by subjecting a cast aluminum piece to predetermined machining and processing, and the heating spacer portion 46 and the water-cooling spacer portion 47 are integrated with each other. In addition, the base spacer 42 is combined with the base body 43 so as to face a side of the heating spacer portion 46 and coupled to the base body 43 via a hexagon socket screw (not illustrated) so as to sandwich an O ring (a sealing member 45).

In this case, the base spacer 42 and the base body 43 can also be integrally molded using cast aluminum or stainless steel. However, since adopting separate components as in the present embodiment reduces dimensions of external shapes, easiness increases in various aspects including machining, management, transportation, and handling during assembly of the components.

Next, the heating spacer portion 46 is annularly formed as a whole and has a rectangular cross section. In addition, the thread stator 24 described earlier is combined with and fixed to the heating spacer portion 46 in a state that enables heat transfer.

A heater 48 for heating and a temperature sensor 51 such as that shown in FIG. 2B are mounted to the heating spacer portion 46. Among these components, the heater 48 is inserted to the heating spacer portion 46 from outside and fixed to the heating spacer portion 46 via a heater mounting tool 50 having a plate material 50 a, a hexagon socket screw 50 b, and the like. The heater 48 varies an amount of heat generation by energization control. In addition, the heater 48 transfers generated heat to the heating spacer portion 46 and raises the temperature of the heating spacer portion 46. In this case, an arrangement of the heater 48 is given due consideration so that the heater 48 can approach the thread stator 24 and heat the thread stator 24 in an efficient manner.

In addition, in the present embodiment, there are two heaters 48 which are arranged at approximately 180-degree intervals in the heating spacer portion 46. However, the present disclosure is not limited to this configuration and the number of the heaters 48 can be increased or reduced. Nevertheless, heating can be performed more efficiently when, for example, the number of the heaters 48 is increased to four and the heaters 48 are arranged at 90-degree intervals.

The temperature sensor 51 described earlier is inserted to the heating spacer portion 46 from outside and fixed via a temperature sensor mounting tool 53. In other words, the temperature sensor 51 is attached to a same component (a single component) as the heater 48. In addition, the sensor mounting tool 53 has a similar structure to the heater mounting tool 50 described earlier and has a plate material 53 a, a hexagon socket screw 53 b, and the like.

In the present embodiment, there are two temperature sensors 51 which are arranged at approximately 180-degree intervals in the heating spacer portion 46. In addition, the temperature sensors 51 are arranged at approximately center of a phase related to the arrangement of the heater 48 (approximately center of the two heaters 48) and are lined up in a single row in a circumferential direction at 90-degree intervals together with the heaters 48. Furthermore, the temperature sensors 51 are arranged so as to approach the thread stator 24 as much as possible and is configured to detect the temperature of the heating spacer portion 46 having been heated by the heater 48 at a position close to the thread stator 24. In this case, as the temperature sensors 51, for example, various general sensors such as a thermistor can be adopted.

The water-cooling spacer portion 47 described earlier is molded in an annular shape as a whole and is positioned in an upper part in the drawing (in an area on the intake side) with respect to the heating spacer portion 46 that constitutes a base. In addition, the water-cooling spacer portion 47 has a larger outer diameter and a larger inner diameter than the heating spacer portion 46 and protrudes in a flange shape toward an outer side in the radial direction.

Furthermore, the upper end portion 29 b of the water-cooling spacer portion 47 is machined so as to be thinner than other portions of the water-cooling spacer portion 47 and protrudes upward in an erected-wall shape. In addition, the upper end portion 29 b of the water-cooling spacer portion 47 is configured to penetrate to an inner side of the intake-side casing 14 a and fit with the intake-side casing 14 a via the sealing member 41.

When compared with the heating spacer portion 46, the water-cooling spacer portion 47 is machined so as to be thinner than the heating spacer portion 46 as a whole and protrudes to an area on an outer side in the radial direction of the heating spacer portion 46. In addition, in a boundary portion 52 between the heating spacer portion 46 and the water-cooling spacer portion 47, a right-angle notched portion 54 on an outer side and an inclined tapered portion 56 on an inner side approach each other so as to retain a suitable thickness.

In other words, on an outer side of the boundary portion 52 (an outer side of the main body casing 14), an outer circumferential surface 46 a of the heating spacer portion 46 and a lower surface 47 a of the water-cooling spacer portion 47 are machined so as to form the notched portion 54 in a mutually orthogonal relationship in a cross section. In addition, on an inner side of the boundary portion 52 (an inner side of the main body casing 14), machining is obliquely performed so that an inner diameter gradually increases from the side of the heating spacer portion 46 toward the side of the water-cooling spacer portion 47 to form the tapered portion 56.

An upper surface 46 b of the heating spacer portion 46 which connects to the tapered portion 56 is positioned on approximately the same plane as the lower surface 47 a of the water-cooling spacer portion 47 described above. In addition, a positional relationship regarding the axial direction between the notched portion 54 and the tapered portion 56 is set such that the notched portion 54 is relatively positioned on a lower side (an exhaust side) and the tapered portion 56 is relatively positioned on an upper side (an intake side).

Forming the boundary portion 52 in such a shape enables the heating spacer portion 46 and the water-cooling spacer portion 47 to seamlessly connect to each other via an area (the boundary portion 52 to act as a thermal conduction portion) which is sandwiched in a bottleneck shape. In addition, by providing the boundary portion 52 that realizes such a narrow neck shape, a conduction path of heat can be narrowed while maintaining favorable thermal conduction by integrating a plurality of components into a single component.

In this case, while the water-cooling spacer portion 47, the heating spacer portion 46, and the boundary portion 52 are integrated into a single component, various interpretations can be made with respect to a subordinate-superior relationship or regions of these components. For example, the boundary portion 52 can be considered to belong to (or constitute a part of) any one of the water-cooling spacer portion 47 and the heating spacer portion 46.

In addition to the above, the boundary portion 52 can also be considered to partially belong to both the water-cooling spacer portion 47 and the heating spacer portion 46. Furthermore, the boundary portion 52 can be considered to constitute a region that is independent from both the water-cooling spacer portion 47 and the heating spacer portion 46 in the base spacer 42. Moreover, a continuous form created by the heating spacer portion 46, the boundary portion 52, and the water-cooling spacer portion 47 can also be referred to, for example, a gooseneck shape.

A water-cooling tube 49 that is a stainless steel tube is embedded (cast-in) in the water-cooling spacer portion 47 so as to extend in a circumferential direction. The water-cooling tube 49 is arranged so as to approach the boundary portion 52. Cooling water is supplied inside the water-cooling tube 49 via a pipe joint (not illustrated), and the cooling water flows inside the water-cooling tube 49 while drawing heat of the water-cooling spacer portion 47 and is guided out from the main body casing 14. The water-cooling spacer portion 47 is cooled as the cooling water is circulated in this manner. In addition, although not illustrated, a flow rate of the cooling water in the water-cooling tube 49 is controlled by opening and closing of a solenoid valve (switching the solenoid valve on and off).

A state of heating by the heater 48 is detected by the temperature sensor 51 that is a thermistor or the like attached at a predetermined position and managed via feedback control by the TMS (Temperature Management System). The TMS is a control method for controlling cooling by the cooling water that flows through the water-cooling tube 49 and heating by the heater 48 and maintaining a temperature of the base spacer 42 and a periphery thereof to a predetermined value (for example, around 70° C.) suitable for exhausting gas.

In other words, gas (process gas) taken into the turbo-molecular pump 10 may be introduced in a high-temperature state into the turbo-molecular pump 10 in order to enhance reactivity. In addition, in some cases, such a gas may cause a product (deposited material) to be deposited in the exhaust system such as the thread groove pump mechanism portion 18 once the gas is cooled to be exhausted and drops to or below a certain temperature.

Furthermore, the deposited material may narrow a flow path of gas and cause a decline in performance of the turbo-molecular pump 10. However, performing temperature control by the TMS described earlier maintains the temperature of the exhaust system at a suitable level and prevents deposited material from being created due to an excessive temperature drop of the gas.

A high temperature setting of the TMS discourages products from being deposited. However, an excessively high temperature setting may adversely affect an electric system and peripheral components. When the temperature inside the main body casing 14 excessively rises, a semiconductor memory (not illustrated) in an electronic circuit is affected and may conceivably lead to, for example, loss of data related to maintenance information such as a pump activation time and an error history.

When data related to maintenance information is lost, a timing of maintenance and inspection, a timing of replacement of the turbo-molecular pump 10, and the like can no longer be determined and operations of the turbo-molecular pump 10 are hindered. Therefore, when the temperature inside the main body casing 14 (more precisely, the temperature of an area where the temperature sensor is installed) reaches an upper limit of a permissible range, a solenoid valve (a cooling water valve, not illustrated) that connects to the water-cooling tube 49 is switched on and cooling by the cooling water is performed.

Heat of the heater 48 is conducted inside the heating spacer portion 46 and transferred to the side of the water-cooling spacer portion 47 via the boundary portion 52. In the boundary portion 52, the notched portion 54 and the tapered portion 56 are provided adjacent to each other as described earlier and a path of thermal conduction has been narrowed down. Therefore, a thermal resistance by the boundary portion 52 is large and an amount of heat that is conducted from the heating spacer portion 46 to the water-cooling spacer portion 47 is kept to a minimum amount.

In addition, the temperature of the heating spacer portion 46 is unlikely to be transferred to the water-cooling spacer portion 47, and cooling by the cooling water in the water-cooling tube 49 is prevented from being hindered by the temperature of the heating spacer portion 46. As a result, cost reduction by integrating the heating spacer portion 46 and the water-cooling spacer portion 47 into a single component can be realized while maintaining preferable thermal conduction characteristics.

Furthermore, in the present embodiment, on/off states of the heater 48 and on/off states of the cooling water valve (not illustrated) are controlled relative to a predetermined temperature (for example, around 70° C.). In addition, as described earlier, since the temperature sensor 51 is arranged so as to approach the thread stator 24 as much as possible, the temperature of the thread stator 24 can be adjusted in an efficient manner. Therefore, the thread stator 24 on which products are readily deposited can be easily managed at a predetermined temperature (for example, around 70° C.) which is a control target.

In addition, since the temperature sensor 51 is arranged approximately halfway between the two heaters 48, the distances to both heaters 48 are the same. Therefore, a bias is less likely to occur in temperature detection and temperatures can be detected in an even and accurate manner. Furthermore, the temperature of the heating spacer portion 46 can be maintained at a predetermined temperature (for example, around 70° C.) or higher in a highly accurate and uniform manner.

In the present embodiment, the temperature sensor 51 is provided in the heating spacer portion 46. However, the temperature sensor 51 is not limited to this configuration and can also be provided in the water-cooling spacer portion 47 in addition to the heating spacer portion 46. In addition, the on/off states of the cooling water valve (not illustrated) can be controlled relative to a separately-set predetermined temperature (for example, a temperature that is sufficiently lower than 70° C.). By also providing the temperature sensor 51 in the water-cooling spacer portion 47, temperature management of the heating spacer portion 46 and the water-cooling spacer portion 47 can be performed with higher accuracy.

FIGS. 3A to 3C show comparison among three types of heating and cooling structures in which a relationship between the heating spacer portion 46 and the water-cooling spacer portion 47 has been differentiated. Hereinafter, by citing a heating and cooling structure of a different type from the first embodiment of the present disclosure shown in FIGS. 1, 2A, and 2B as an example and comparing the heating and cooling structure with the heating and cooling structure according to the first embodiment, features of the turbo-molecular pump 10 according to the first embodiment and a heating and cooling structure according to a second embodiment will be described. It should be noted that, in heating and cooling structures that differ from the first embodiment of the present disclosure, portions similar to those of the first embodiment will be denoted by same signs and descriptions will be omitted when appropriate.

FIG. 3A at the left end of FIG. 3 shows a type with a conventional structure that includes the heating spacer portion 46 and the water-cooling spacer portion 47 as separate components. In addition, in the conventional structure, the heating spacer portion 46 and the water-cooling spacer portion 47 are airtightly coupled to each other via an O-ring (a sealing member). Furthermore, in the conventional structure, the heating spacer portion 46 is integrally molded with the base body 43. Moreover, the water-cooling spacer portion 47 is machined as a cast aluminum piece, and the heating spacer portion 46 and the base body 43 are machined by shaving from a wrought aluminum material.

In the case of a turbo-molecular pump provided with a conventional heating and cooling structure such as that shown in FIG. 3A, since the heating spacer portion 46 and the water-cooling spacer portion 47 are separate components that are placed apart from each other, there is no direct conduction of heat. Therefore, thermal resistance is high and heat insulating properties are excellent.

However, since the heating spacer portion 46 is integrally molded with the base body 43, a large component is to be included in the structure, resulting in increased external dimension and weight of the components. In addition, machining cost of the component that integrates the heating spacer portion 46 and the base body 43 (in this case, the component can be referred to as a “base spacer”) increases. Furthermore, difficulty increases in various aspects including management and transportation for storing the large-sized base spacer and handling of the base spacer during assembly.

FIG. 3B shows a heating and cooling structure according to the second embodiment of the present disclosure which represents a type in which the heating spacer portion 46 and the water-cooling spacer portion 47 have been integrated into a single component. The heating and cooling structure according to the second embodiment has been created as a first enhancement proposal with respect to the conventional structure described above. In addition, while FIG. 3C shows the heating and cooling structure according to the first embodiment (a heating and cooling structure similar to that shown in FIGS. 1, 2A, and 2B), the first embodiment related to FIG. 3C has been created as a further enhancement proposal with respect to the second embodiment shown in FIG. 3B.

In the second embodiment shown in FIG. 3B, a base spacer 62 which includes the heating spacer portion 46 and the water-cooling spacer portion 47 and which is molded as a single component is coupled to the base body 43 so as to sandwich an O-ring (the sealing member 45) in a similar manner to the first embodiment described earlier. In addition, while the second embodiment includes a boundary portion 72 that constitutes a thermal conduction portion in a similar manner to the first embodiment, the boundary portion 72 has a shape in which right-angle notched portions 54 and 74 obliquely face each other on inner and outer sides in the radial direction in a cross section.

Furthermore, the upper surface 46 b of the heating spacer portion 46 is positioned above (on an intake side of) the lower surface 47 a of the water-cooling spacer portion 47 in the drawing. In addition, an inner circumferential surface 47 b of the water-cooling spacer portion 47 forms an erected wall that rises approximately vertically from the upper surface 46 b of the heating spacer portion 46. Furthermore, a flat inner circumference-side upper surface 47 c that extends in the radial direction is formed between the inner circumferential surface 47 b of the water-cooling spacer portion 47 and the upper end portion 29 b of the water-cooling spacer portion 47.

In the second embodiment configured as described above, since the heating spacer portion 46 and the water-cooling spacer portion 47 are integrated, when compared with a conventional structure illustrated in FIG. 3A, a weight and an external shape of components on a side of the base body 43 can be distributed more on the side of the water-cooling spacer portion 47. As a result, with respect to the components constituting the exhaust side, external dimensions and a weight balance of the components can be more equalized (optimized) and easiness increases in various aspects including machining, management, and transportation of the components, and handling of the components during assembly.

An analysis of a thermal resistance between the heating spacer portion 46 and the water-cooling spacer portion 47 according to the second embodiment described above and a comparison with a conventional structure revealed that, while thermal conduction occurs slightly more readily than the conventional structure, costs related to machining of components and the like are reduced. More specifically, assuming that a thermal resistance and cost in the conventional structure shown in FIG. 3A are represented as 100% as a reference, a thermal resistance according to the second embodiment is 60% and cost according to the second embodiment is 70%. In other words, the heating and cooling structure according to the second embodiment turns out to be a type which promotes cost reduction while keeping a decline in characteristics related to thermal resistance to a certain level as compared to the conventional structure.

It should be noted that, as a numerical analysis of thermal resistances related to the conventional structure and the second embodiment, simulations have been performed by replacing a relationship between a capacity of the heater 48 (a heating state) and a state of control of the cooling water that flows through the water-cooling tube 49 with a relationship between an average temperature of the thread stator 24 (an external thread) and an on-time related to the cooling water (a solenoid valve open time).

FIG. 4 shows, in a simplified manner, a relationship between a temperature (an average temperature) T of a measurement area in the thread stator 24 and a solenoid valve open time. On/off states of the solenoid valve are shown in a lower half of the drawing, and a variation in the temperature T of the thread stator 24 is shown in an upper half of the drawing. The temperature rises gradually when the solenoid valve is switched off and the temperature drops gradually when the solenoid valve is switched on.

A target temperature with respect to the thread stator 24 is set to 70° C. In addition, temperature control of the heater 48 is performed so that the temperature of 70° C. is maintained even in a no-load state where there is no gas flow. In other words, this situation may be fitted to FIG. 4 and described as: the solenoid valve being switched on and off so that a waveform of the temperature T is within a range of 70 to 75° C.

Next, with respect to the first embodiment shown in FIG. 3C, due to the structure described earlier and shown in FIGS. 1, 2A, and 2B, a thermal resistance relative to the conventional structure is 80% and cost relative to the conventional structure is 70%. In other words, the thermal resistance more closely approaches the conventional structure in FIG. 3A than the second embodiment shown in FIG. 3B and the cost is the same as the second embodiment. Therefore, the heating and cooling structure according to the first embodiment can be described as a type which keeps a decline in thermal resistance to an even lower level while realizing equally low cost as compared to the second embodiment.

It should be noted that the present disclosure is not limited to the first embodiment and the second embodiment described above and various modifications can be made without departing from the spirit and scope of the disclosure. For example, with respect to the first embodiment and the second embodiment of the present disclosure, shapes and dimensions of the boundary portions 52 and 72 affect thermal conduction between the heating spacer portion 46 and the water-cooling spacer portion 47. In addition, the shapes and the dimensions of the boundary portions 52 and 72 can be changed to optical shapes and dimensions in accordance with a target temperature.

In addition, in the first embodiment and the second embodiment of the present disclosure, a cast aluminum piece is adopted as the base spacer 42 that includes the heating spacer portion 46 and the water-cooling spacer portion 47. Therefore, compared to forming the base spacer 42 by, for example, shaving stainless steel, machining is easier and cost is kept low. However, the base spacer 42 is not necessarily limited to a cast aluminum piece and, depending on the situation, the base spacer 42 may be made from stainless steel.

Adopting a cast aluminum piece as the base spacer 42 results in lower rigidity and strength as compared to adopting stainless steel. In addition, the fact that the boundary portions 52 and 72 have been narrowed down also contributes to lower rigidity and strength of the base spacer 42. However, by casting the water-cooling tube 49 made of stainless steel in a vicinity of the boundary portions 52 and 72 in the water-cooling spacer portion 47 of the base spacer 42 as in the first embodiment and the second embodiment of the present disclosure, the base spacer 42 and, particularly, the vicinity of the boundary portion 72 can be reinforced. 

What is claimed is:
 1. A vacuum pump, comprising: a pump mechanism portion in which a stator blade and a rotor blade are formed; a casing which encloses the pump mechanism portion; a motor for rotating the rotor blade; and a vacuum pump constituent component which is capable of thermal conduction between a heating portion and a cooling portion having been integrally molded, wherein the vacuum pump constituent component is provided with a boundary portion formed so that a cross section thereof assumes a narrow neck shape between the heating portion and the cooling portion.
 2. The vacuum pump according to claim 1, wherein the boundary portion is formed between a notched portion on an outer side and a tapered portion on an inner side of the vacuum pump constituent component.
 3. A vacuum pump constituent component which is capable of thermal conduction between a heating portion and a cooling portion having been integrally molded and which is provided with a boundary portion having been molded so that a cross section thereof assumes a narrow neck shape between the heating portion and the cooling portion.
 4. The vacuum pump constituent component according to claim 3, wherein the boundary portion is formed between a notched portion on an outer side and a tapered portion on an inner side. 